Updated UnicornHat scrolling text library

I finally found the time to update the character definitions for the Pimoroni UnicornHat scrolling text library that I wrote before Christmas.

In addition to fixing the spacing issue with the hash, I've added the dollar sign $, asterix *, normal brackets(), equals = and plus sign + along with the two chevrons >< and double quotes ". So now you can produce algebra!

The code is available on Github.